This application claims the priority of Korean Patent Application No. 2003-9414, filed on Feb. 14, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to planar display devices, and more particularly, to a plasma display panel (hereinafter, referred to as PDP) comprising an ultraviolet-to-visible ray converter.
2. Description of the Related Art
PDPs are planar image display devices, in which a gas, such as Ne+Xe, is injected into a space that is defined by a front glass substrate, a rear glass substrate, and partitions between the front and rear glass substrates, ultraviolet (UV) rays emitted from Xe gas due to application of a voltage to anodes and cathodes are converted into visible rays by using fluorescent substances, and the visible rays are used as display rays.
PDPs can be the most easily enlarged, among planar displays, such as liquid crystal displays (LCDs), field emission displays (FEDs), and electro-luminescence displays (ELDs).
PDPs are anticipated to have a high luminance and a high luminous efficacy, by plasma production due to the employment of an efficient electrode structure and an efficient driving circuit, by an improvement in the efficiency of UV emission from plasma, by an improvement in the efficiency of conversion of visible rays by fluorescent substances, and by other measures.
FIG. 1 is an exploded perspective view of a conventional AC type PDP. Referring to FIG. 1, the conventional AC type PDP includes a front glass substrate 10 and a rear glass substrate 12, which faces the front glass substrate 10 in parallel. A filter set 30 is installed over the front glass substrate 10 and blocks off infrared rays (IR), electromagnetic interference (EMI), and the like that are emitted from the PDP. The filter set 30 is comprised of black stripe areas 32a and filtering areas 32b. The filtering areas 32b receive and filter out filtering elements, such as, IR or EMI generated from discharge cells. The black stripe areas 32a correspond to barrier ribs 26 to be described later, in a one-to-one correspondence, and prevent the filtering elements generated from a discharge cell from being introduced into another discharge cell. First and second discharge sustaining electrodes 14a and 14b are arranged in parallel on a surface of the front glass substrate 10 that faces the rear glass substrate 12. The first and second discharge sustaining electrodes 14a and 14b are transparent. As shown in FIG. 2, there is a gap (d) between the first and second discharge sustaining electrodes 14a and 14b. A first bus electrode 16a is formed on the first discharge sustaining electrode 14a, and a second bus electrode 16b is formed on the second discharge sustaining electrode 14b. The first and second bus electrodes 16a and 16b prevent a voltage from being lowered by a resistance during discharge. The first and second discharge sustaining electrodes 14a and 14b and the first and second bus electrodes 16a and 16b are covered with a first dielectric layer 18, which is covered with a protective film 20. The protective film 20 protects the first dielectric layer 18, which is weak to discharge, so that the PDP can stably operate for a long period of time. Also, the protective film 20 lowers a discharge voltage by emitting secondary electrons in great quantities during discharge. A magnesium oxide (MgO) film is widely used as the protective film 20.
Address electrodes 22 for addressing pixels are installed on the rear glass substrate 12. Since one address electrode 22 is included in one discharge cell, one pixel has three address electrodes 22. The address electrodes 22 are parallel to one another and perpendicular to the first and second discharge sustaining electrodes 14a and 14b. A second dielectric layer 24, with which the address electrodes 22 are covered, is formed on the rear glass substrate 12 and performs a light reflection. A plurality of barrier ribs 26 are arranged at regular intervals on the second dielectric layer 24. More specifically, the barrier ribs 26 are placed on portions of the second dielectric layer 24 that exist between adjacent address electrodes 22. From the viewpoint of the second dielectric layer 24, the address electrodes 22 alternate with the barrier ribs 26. The barrier ribs 26 adhere to the protective film 20 on the front glass substrate 10 while the front and rear glass substrates 10 and 12 are joining. Fluorescent layers 28a, 28b, and 28c are coated between adjacent barrier ribs 26 such as to cover the portions of the second dielectric layer 24 defined therebetween and lateral surfaces of the barrier ribs 26. The first, second, and third fluorescent layers 28a, 28b, and 28c are excited by UV rays and thus emit red (R), green (G), and blue (B) light, respectively.
FIG. 3 is a cross-section of a unit discharge cell of the PDP, taken in a direction perpendicular to the address electrodes 22. In FIG. 3, reference character A1 denotes UV rays with 147 nm and 173 nm wavelengths that are emitted from a plasma forming area 32 and projected toward the fluorescent layers 28a, 28b, and 28c. The rays A1 are referred to as first UV rays hereinafter. Reference character A2 denotes visible rays emitted from the fluorescent layers 28a, 28b, and 28c excited by the first UV rays A1, while the fluorescent layers are being stabilized. Reference character A3 denotes UV rays with 147 nm and 173 nm wavelengths that are emitted in the direction opposite to the direction of emission of the first UV rays A1. The rays A3 are referred to as second UV rays hereinafter.
As shown in FIG. 3, in a conventional PDP, some of the UV rays emitted from the plasma forming area 32 within a cell, that is, the second UV rays A3, are absorbed by the front glass substrate 10. In other words, in a conventional PDP, the fluorescent layers 28a, 28b, and 28c are excited not by most of the UV rays emitted from the plasma forming area 32 but by only some of the UV rays.
The visible rays emitted from the fluorescent layers 28a, 28b, and 28c increase in proportion to the number of UV rays projected onto the fluorescent layers 28a, 28b, and 28c. As described above, in a conventional PDP, since the number of UV rays projected onto the fluorescent layers 28a, 28b, and 28c is restricted, the number of visible rays emitted from the fluorescent layers 28a, 28b, and 28c is also restricted. As a result, the luminance and efficiency of a conventional PDP are lowered.